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CA report for fence.pdfi- (,D 2 0 0Alll 4-�Cp ., ..... .....„.. ,,,,,,.... ... ... ......,. ......... ..,.... .. .� ...., ,,,, ..,. ,...,,�,...,,. .. .u. a „.,...,... RT .......OSS Gf i p lr lr� i P 9� January 22, 2016 n 0� v �a 1 1AN 2 2 2016 BUILDING DEPARTMENT Mr. Jim Bagby (ITY CSE EDMOtlDe 9131 184th Street Southwest Edmonds, WA 98026 Re: Bagby Residence Critical Areas Review 12798-01 Dear Mr. Bagby: This letter presents our findings from a review of the critical areas on and around the Bagby residence, located at 9131 184th Street Southwest in Edmonds, Washington (the site). In a plan review comments letter dated November 24, 2015, the City of Edmonds requested a critical areas review (CAR) for the fence construction project you (the homeowner) proposed. The City requested the review include geologic hazards, stream typing, and buffer determination. Methods Our review included visiting the site (on January 8, 2016) and reviewing existing information sources, including Washington Department of Natural Resources (WDNR) Forest Practices Application Review System (FPARS) online stream type mapping; Washington Department of Fish and Wildlife (WDFW) Priority Habitat and Species (PHS) on the Web; Snohomish County Permit, Planning, and Zoning Map; WDNR's Interactive Geologic Map (www.fortress.wa.gov/dnr/geology); the Edmonds City Code and Community Development Code (ECDC); aerial photos; City of Edmonds plan review comments (20T5 - T486); and City of Edmonds CAR CRA2015OTL4, dated November 23, 2015. Background The proposed project consists of constructing a fence at or near the surveyed parcel boundary. The proposed fence along the east side of the property will partially replace an existing chain-link fence at the top of the natural slope and along the top of an existing rock wall. Additional new fence segments are proposed along the remaining borders of the property. Areas of concern for the City include possible steep slopes near the east and west of the proposed project and a small runoff feature near the southwest boundary of the site, which was flowing both on the day of the City's inspection and our site visit. See Attachment 1 for a site plan, Attachment 2 for construction plans, and Attachment 3 for site photographs. 190 W Dayton Street, Suite 201 Edmonds, Washington 98020 Fax 425 778, 9417 Tel 425 775,4682 Bagby Critical Areas Review 12798-01 January 22, 2016 Page 2 Geologic Hazards This section addresses Item 1 of the City's plan review comments letter. Site Visit Geotechnical Observations. During our site visit, we observed existing site conditions and the plan limits of the proposed fence construction, as summarized below: U The associated LiDAR map indicates that the eastern third of the subject site slopes gradually downward from east to west at a grade of approximately 30%. The middle third, where the existing structures are located, is fairly level. The western third of the parcel falls away more steeply to the west at a grade of approximately 35%. ■ Soils throughout the site are identified as Alderwood Gravelly sandy loam (15% to 25% slope). As a result, the slopes in excess of 15% are classified as potential erosion hazards and the western slope that exceeds 35% is a potential landslide hazard area. a We did not observe soil movement or erosion in the project area. Review of Existing Site Data. We reviewed the previously mentioned existing site information to learn about existing conditions and the proposed construction. We also reviewed WDNR's Interactive Geologic Map to determine subsurface soil conditions. The site is mapped as being within the Quaternary Vashon till, of the Frasier Glaciation. Our observations of near -surface soils at the site are generally consistent with those indicated on the geologic map. ECDC Geologic Hazard Review. We reviewed the ECDC sections defining geologic hazards (23.80.000 through 23.80.070) to determine conditions applicable to the proposed site work, as described below: a Landslide Hazard Areas. In our opinion, the proposed work will not adversely affect the small steep slopes in the project area, for the following reasons: • The proposed fence construction would only minimally alter the existing conditions of the critical area or its buffer. 0 Our observations of the top and toe of existing slopes do not indicate signs of instability. . Because of its small footprint, the proposed work would not increase loads on the slopes; work near the eastern site boundary would replace an existing fence. a Erosion Hazard. Areas surrounding the proposed construction area are vegetated; maintaining the vegetation well would reduce erosion potential. The construction contractor should use standard temporary erosion and sedimentation control practices (e.g., straw wattles between the work area and slopes) during construction activities that expose bare soil, as needed, to avoid off-site runoff of turbid water. After construction, landscape restoration would likely prevent long-term erosion. Bagby Critical Areas Review January 22, 2016 12798-01 Page 3 Seismic Hazards. We did not observe subsurface conditions such as shallow groundwater in loose clean sand that would lead to liquefaction. In addition, the site subsurface geology is mapped as Vashon Till, which is typically dense and therefore less susceptible. In our opinion, liquefaction hazards do not apply to this site. At any rate, ECDC 23.80.040 allows fences in seismically hazardous zones. Stream Typing and Buffer Determination A very small -runoff feature near the southwest boundary of the site was identified on the day of the site visit. The source of this feature is not visible, but is likely nearby stormwater runoff from 184th Street SW, rain gutters, and drainage lines. The runoff feature terminates underground near the western Bagby property boundary. Local topography suggests that during storm events the feature may contribute to another water feature near Olympic View Drive, but the Bagby runoff feature is not visible in the approximately 650 feet between the Bagby property and Olympic View Drive. The Bagby runoff feature only contains water after large precipitation events. It is not mapped by WDNR, WDFW PHS on the Web, or Snohomish County Permit, Planning, and Zoning Map. Considering this information, we believe the runoff feature is a collection area where stormwater runoff occasionally settles, not a regulated stream. Conclusions Our geologic and geotechnical evaluation indicates that the proposed project will not alter the existing small steep slopes if basic construction practices and precautions are followed. This project should not result in increased landslide hazard or erosion hazard. Seismic hazards are not applicable. Our stream investigation found that the water feature on the site is generated from stormwater runoff and is not a regulated stream. Use of This Report Work for this project was performed, and this letter prepared, in accordance with professional practices generally accepted at the time our work was performed for work of similar nature done in the same or similar localities and under similar conditions. This letter is intended for the exclusive use of the property owner for specific application to the referenced site. This analysis applies only to the proposed project described above. New analyses and permits must be obtained for any alterations or for any �6 Bagby Critical Areas Review January 22, 2016 12798-01 Page 4 future projects on the site. This letter was prepared in general accordance with our proposal dated January 11, 2016. It is not a legal opinion. No other warranty, express or implied, is made. Sincerely, HART CROWSER, INC. JIM SHANNON Fisheries and Wetland Scientist Attachments: Attachment 1 Site Plan Attachment 2 Design Plan Supplied by Homeowner Attachment 3 Site Photographs AARON WISHER, LG Senior Project Geologist R:\NOTEBOOKS\1279801_Bagby Critical Areas Review\Deliverables\Letters\Critical Areas Review Letter.docx AT TACH SNIT 1 Site Flan 12798-01 January 22, 2016 ATTACHMENT 2 Design Plan Supplied by Homeowner OW 12798-01 AWJanuary22, 2016 ATTACHMENT A — FENCE PLOT PLAN PROPERTY OWNER — James Bagby & Mary VanCitters-Bagby PROPERTY ADDRESS — 9131 184" St. SW, Edmonds, WA 98026 PARCEL NUMBERS — 27041800201100, 00565600101700 PROJECT DESCRIPTION — Six (6) foot chain link fence to be constructed in two phases. Phase 1 (to be completed upon permit approval) — east property line. Phase 2 (to be completed Summer 2016) — remaining property lines with automatic gate over driveway. N/y7e � lr Il T i to5. q w" J �4 Ft-?,�ct L -I IJC- PU 5 I I F - - - -- - .- . . . ... . - Site Photographs 12798-01 January 22, 2016 Hart Crowser 12798-01 Looking north toward carport and slightly downslope. Looking southeast from neighboring property toward water feature (not in view), Hart Crowser 12798-01 Buried pipe from roof drain (neighbor). Property corner at northwest of parcel showing native vegetation growth. Hart Crowser 12798-01 Current growth on steep slope north and northeast of house. Current growth along northern parcel boundary showing neighboring fence. Hart Crowser 12798-01 Rock wall at northeast corner of property with fence at top of slope. Looking south along top of east slope, showing existing fence. Hart Crowser 12798-01 General vegetation at upper slope.. Looking east toward top of slope. Poles show position of new fencing to be installed. Hart Crowser 12798-01 Looking down slope toward greenhouse. Storm drain at southeast corner of carport. Flow direction to top of image (north), Hart Crowser 12798-01 Water feature showing flow to top of image (west) Water feature showing flow to top of image (west)